Electronics Combinational Logic Circuits Questions and Answers

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Showing 10 of 29 questions
Q21
Which circuit converts binary to decimal?
  • A Multiplexer
  • B Encoder
  • C Decoder
  • D Demultiplexer
Answer: Option C
Explanation: Decoder converts binary input to activated output line.
Q22
What is the carry generate function in carry lookahead adder?
  • A P = A XOR B
  • B G = A AND B
  • C S = A XOR B XOR Cin
  • D Cout = A OR B
Answer: Option B
Explanation: G = A AND B generates carry regardless of carry-in.
Q23
In a 4-bit comparator, what indicates A > B?
  • A A3B3' + A2B2' + A1B1' + A0B0'
  • B A3B3' only
  • C All bits equal
  • D A0B0' only
Answer: Option A
Explanation: A>B when higher order bits are greater or equal with at least one bit greater.
Q24
What is the purpose of a demultiplexer?
  • A Selects inputs
  • B Routes input to one output
  • C Encodes data
  • D Stores data
Answer: Option B
Explanation: Demultiplexer routes single input to one of multiple outputs.
Q25
How many AND gates are needed for a 4-to-16 decoder?
  • A 4
  • B 8
  • C 16
  • D 32
Answer: Option C
Explanation: 4-to-16 decoder requires 16 AND gates (one per output)
Q26
What is the sum output expression for a full adder?
  • A A AND B OR Cin
  • B A XOR B XOR Cin
  • C A OR B AND Cin
  • D A NAND B XOR Cin
Answer: Option B
Explanation: Sum = A XOR B XOR Cin
Q27
Which circuit can be used as a universal logic function generator?
  • A Decoder
  • B Multiplexer
  • C Encoder
  • D Demultiplexer
Answer: Option B
Explanation: MUX can implement any logic function with proper select lines.
Q28
What is the propagation delay in combinational circuits?
  • A Setup time
  • B Hold time
  • C Clock period
  • D Time from input to output change
Answer: Option D
Explanation: Time from input change to output stabilization.
Q29
Which is NOT a combinational circuit?
  • A Adder
  • B Multiplexer
  • C Decoder
  • D Counter
Answer: Option D
Explanation: Counter has memory element (flip-flops)

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